Virgin Galactic's WhiteKnightTwo and SpaceShipTwo aircraft will be doing the world a favor when they start flying paying passengers into space: they'll be carrying sensors aboard to monitor greenhouse gases at a little-monitored altitude. The National Oceanic and Atmospheric Administration has just signed a deal with Virgin to let it install sensors on the two vehicles, since it turns out that they will be one of the few aircraft that fly at around 50,000 feet. Most aircraft, with the exception of the sadly gone Concorde, fly below this altitude, and scientists would like to get their hands on air data from this height to help with environmental monitoring.Luckily Scaled Composites, builders of the aircraft and spacecraft, planned for this sort of opportunity and designed their air-data probe systems, usually used just for avionics, to allow for other sensors to be attached in the hope that exactly this sort of science opportunity would come along. The sensors will look for CO2 and other greenhouse gases, and will be aboard the 200-odd practice flights needed for testing and certification. After that program, Virgin and NOAA will decide if the equipment will go onto the commercial space flights alongside paying passengers. [NewScientist]